welche nährstoffe fehlen bei haarausfall — what are common causes?

The question of which nutrient deficiencies cause hair loss is complex. Common suspects include iron, zinc, biotin, vitamin D, and selenium – but the evidence is mostly weak to moderate. Iron deficiency (especially in women with heavy menstruation) may contribute to diffuse hair loss, but a causal link is not always proven. Zinc deficiency is associated with brittle hair, yet routine supplementation without confirmed deficiency is not recommended. Biotin deficiency is rare (except with raw egg consumption or certain metabolic disorders) and typically causes brittle nails, not primarily hair loss. Vitamin D deficiency has been linked to alopecia in observational studies, but randomized controlled trials are lacking. Selenium: deficiency is uncommon in Central Europe; excess can actually promote hair loss. Importantly, hair loss has many causes – genetic (androgenetic alopecia), hormonal (thyroid, stress), medication-induced, or inflammatory (e.g., alopecia areata). A blood test for deficiencies can be useful, but without medical evaluation it remains speculative. The provided contexts contain no specific data on hair loss – therefore the evidence level is unclear.